Imaging lens and imaging apparatus

ABSTRACT

An imaging lens includes: an aperture stop; a first lens having a positive refractive power; a second lens having a negative refractive power which is formed in a concave shape on both sides thereof; a third lens having a positive refractive power which is formed in a meniscus shape in which a concave surface is directed toward the side of an object; and a fourth lens having a negative refractive power in which a convex surface is directed toward the object side, which are sequentially disposed from the object side to the image side, wherein the imaging lens satisfies the following conditional expressions (1), (2), (3), (4) and (5): 
       0.40&lt; f 1/| f 2|&lt;0.80  (1)
 
       0.80&lt;| f 2|/ f 3&lt;1.50  (2)
 
       0.90&lt; f/|f 4|&lt;2.00  (3)
 
       2.60&lt;|( R 2− R 3)/ f 1|&lt;4.00  (4)
 
       ν d 1−ν d 2&gt;25.  (5)

FIELD

The present disclosure relates to an imaging lens and an imagingapparatus. More particularly, the present disclosure relates to atechnical field of an imaging lens which is suitable for a small sizedapparatus such as a digital still camera or a mobile phone mounted witha camera including an imaging device, and an imaging apparatus includingthe imaging lens.

BACKGROUND

A mobile phone with an attached camera, a digital still camera or thelike including an imaging device (solid state imaging device) such as aCCD (Charge Coupled Device) or a CMOS (Complementary Metal OxideSemiconductor) has been used as an imaging apparatus.

In such an imaging apparatus, there is demand for miniaturization.Further, in an imaging lens mounted in the imaging apparatus, there isalso demand for a small size and a short total optical length.

Further, in recent years, in a small sized imaging apparatus such as amobile phone with an attached camera, as miniaturization has beenfacilitated and a high pixel density imaging device has been developed,imaging apparatus models mounted with an imaging device of a high pixeldensity which is equivalent to a digital still camera have becomewidespread. Thus, a high pixel density lens performance corresponding tothe high pixel density imaging device is demanded in an imaging lens tobe mounted.

Further, in order to prevent deterioration of image quality due to noisein photographing in dark places, there is demand for a lens with abright F-number.

Under these circumstances, in the related art, the following imaginglenses have been proposed (for example, JP-A-2004-4566,JP-A-2002-365530, JP-A-2002-365531, JP-A-2006-293324, JP-A-2007-219079,and JP-A-2009-69163).

SUMMARY

An imaging lens disclosed in JP-A-2004-4566 has a three-lens structureand a short total optical length is advantageous. However, with thethree-lens structure, it is difficult to satisfy the demand for a highresolution lens due to the high pixel density imaging device asdescribed above and of small chromatic aberration, and to secureexcellent optical performance corresponding to an imaging device with ahigh pixel density.

An imaging lens disclosed in JP-A-2002-365530 and JP-A-2002-365531 has afour-lens structure and is capable of reliably correcting variousaberrations, but has a long total optical length and thus does notsatisfy the demand for miniaturization. Further, since the positiverefractive power of the first lens and the negative refractive power ofthe second lens are strong, the eccentric sensitivity is high andassembly efficiency is lowered, which may result in deterioration ofoptical performance.

An imaging lens disclosed in JP-A-2006-293324 has a four-lens structureand has a high aberration correction capability, but has a long totaloptical length and thus does not satisfy the demand for miniaturization.Further, since a third lens has a convex shape on both sides, it isdifficult to correct aberration. Further, ghosting may occur whenperipheral light beams are totally reflected, which may result indeterioration of optical performance to lower image quality.

An imaging lens disclosed in JP-A-2007-219079 has a four-lens structureand is capable of reliably correcting various aberrations, andparticularly, field curvature, but has a long total optical length andthus does not satisfy the demand for miniaturization. Further, since thesecond lens is formed in a concave meniscus shape in which a convexportion is directed toward the object side, ghosting may occur, whichmay result in deterioration of optical performance so as to lower imagequality. Further, since the refractive power of the second lens is weak,chromatic aberration is not sufficiently corrected, which may causedeterioration of optical performance. In addition, since the positiverefractive power of the third lens and a negative refractive power ofthe fourth lens are strong, the eccentric sensitivity between the firstlens and the second lens is high and assembly efficiency is lowered,which may result in deterioration of optical performance. Furthermore,reflection ghosting occurring in a peripheral section of the fourthlength may enter an imaging device, which may result in deterioration ofoptical performance so as to lower image quality.

An imaging lens disclosed in JP-A-2009-69163 has a four-lens structureand has a high aberration correction capability, but has a long totaloptical length and thus does not satisfy the demand for miniaturization.Further, since the refractive power of the second lens is weak,chromatic aberration is not sufficiently corrected, which may causedeterioration of optical performance. Further, since the positiverefractive power of the third lens and the negative refractive power ofthe fourth lens are strong, the eccentric sensitivity between the firstlens and the second lens is high and assembly efficiency is lowered,which may result in deterioration of optical performance. Furthermore,reflection ghosting occurring in a peripheral section of the fourthlength may enter an imaging device, which may result in deterioration ofoptical performance to lower image quality.

Accordingly, it is desirable to provide an imaging lens and an imagingapparatus which are capable of securing an excellent optical performancecorresponding to a high pixel density imaging device and of achievingminiaturization.

An embodiment of the present disclosure is directed to an imaging lensincluding an aperture stop, a first lens having a positive refractivepower, a second lens having a negative refractive power which is formedin a concave shape on both sides thereof, a third lens having a positiverefractive power which is formed in a meniscus shape in which a concavesurface is directed toward the object side, and a fourth lens having anegative refractive power in which a convex surface is directed towardthe object side, which are sequentially disposed from the object side tothe image side. Here, the imaging lens satisfies the followingconditional expressions (1), (2), (3), (4) and (5):

0.40<f1/|2|<0.80  (1)

0.80<|f2|/f3<1.50  (2)

0.90<f/|f4|<2.00  (3)

2.60<|(R2−R3)/f1|<4.00  (4)

νd1−νd2>25  (5)

where f1 is the focal length of the first lens, f2 is the focal lengthof the second lens, f3 is the focal length of the third lens, f4 is thefocal length of the fourth lens, f is the focal length of an entire lenssystem, R2 is a paraxial curvature radius of a surface on the objectside of the first lens, R3 is a paraxial curvature radius of a surfaceon the image side of the first lens, νd1 is the Abbe number of the firstlens, and νd2 is the Abbe number of the second lens.

With this configuration, focal lengths are appropriately distributedbetween the first lens having the positive refractive power, the secondlens having the negative refractive power, the third lens having thepositive refractive power and the fourth lens having the negativerefractive power, in the imaging lens.

In the above-described imaging lens, it is preferable that the imaginglens satisfy the following conditional expression (6):

0.30<|(R6−R7)/f3|<1.50  (6)

where R6 is a paraxial curvature radius of the surface on the objectside of the third lens, and R7 is a paraxial curvature radius of asurface on the image side of the third lens.

As the imaging lens satisfies the conditional expression (6), the sizeof the paraxial curvature radii of the surface on the object side of thethird lens and the surface on the image side thereof become optimal, andthe difference between the paraxial curvature radii of the surface onthe object side of the third lens and the surface on the image sidethereof is prevented from being large.

In the above-described imaging lens, it is preferable that the aperturestop be disposed between the top of the surface on the object side ofthe first lens and the effective diameter thereof.

As the aperture stop be disposed between the top of the surface on theobject side of the first lens in the optical axis direction and theeffective diameter thereof, the amount of peripheral light entering thefirst lens is increased.

In the above-described imaging lens, it is preferable that the imaginglens satisfy the following conditional expression (7):

3.00<|f4|/D8<7.00  (7)

where D8 is a center thickness of the fourth lens.

As the imaging lens satisfies the conditional expression (7), the centerthickness of the fourth lens becomes optimal.

In the above-described imaging lens, it is preferable that the imaginglens satisfy the following conditional expression (8):

1.00<R4/f2<30.00

where R4 is a paraxial curvature radius of a surface on the object sideof the second lens.

As the imaging lens satisfies the conditional expression (8), the sizeof the paraxial curvature radius of the surface on the object side ofthe second lens becomes optimal.

Another embodiment of the present disclosure is directed to an imagingapparatus including an imaging lens and an imaging device which convertsan optical image formed by the imaging lens into an electrical signal.The imaging lens includes an aperture stop, a first lens having apositive refractive power, a second lens having a negative refractivepower which is formed in a concave shape on both sides thereof, a thirdlens having a positive refractive power which is formed in a meniscusshape in which a concave surface is directed toward the side of anobject, and a fourth lens having a negative refractive power in which aconvex surface is directed toward the object side, which aresequentially disposed from the object side to the image side. Theimaging lens satisfies the following conditional expressions (1), (2),(3), (4) and (5):

0.40<f1/|2|<0.80  (1)

0.80<|f2|/f3<1.50  (2)

0.90<f/|f4|<2.00  (3)

2.60<|(R2−R3)/f1|<4.00  (4)

νd1−νd2>25  (5)

where f1 is the focal length of the first lens, f2 is the focal lengthof the second lens, f3 is the focal length of the third lens, f4 is thefocal length of the fourth lens, f is the focal length of an entire lenssystem, R2 is a paraxial curvature radius of a surface on the objectside of the first lens, R3 is a paraxial curvature radius of a surfaceon the image side of the first lens, νd1 is the Abbe number of the firstlens, and νd2 is the Abbe number of the second lens.

With this configuration, focal lengths are appropriately distributedbetween the first lens having the positive refractive power, the secondlens having the negative refractive power, the third lens having thepositive refractive power and the fourth lens having the negativerefractive power, in the imaging lens of the imaging apparatus.

According to the imaging lens and the imaging apparatus of theembodiment of the present disclosure, it is possible to secure anexcellent optical performance corresponding to an imaging device of ahigh pixel density and to achieve miniaturization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a lens configuration of an imaging lensaccording to a first embodiment;

FIG. 2 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe first embodiment;

FIG. 3 is a diagram illustrating a lens configuration of an imaging lensaccording to a second embodiment;

FIG. 4 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe second embodiment;

FIG. 5 is a diagram illustrating a lens configuration of an imaging lensaccording to a third embodiment;

FIG. 6 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe third embodiment;

FIG. 7 is a diagram illustrating a lens configuration of an imaging lensaccording to a fourth embodiment;

FIG. 8 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe fourth embodiment;

FIG. 9 is a diagram illustrating a lens configuration of an imaging lensaccording to a fifth embodiment;

FIG. 10 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe fifth embodiment;

FIG. 11 is a diagram illustrating a lens configuration of an imaginglens according to a sixth embodiment;

FIG. 12 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe sixth embodiment;

FIG. 13 is a diagram illustrating a lens configuration of an imaginglens according to a seventh embodiment;

FIG. 14 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe seventh embodiment;

FIG. 15 is a diagram illustrating a lens configuration of an imaginglens according to an eighth embodiment;

FIG. 16 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe eighth embodiment;

FIG. 17 is a diagram illustrating a lens configuration of an imaginglens according to a ninth embodiment;

FIG. 18 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe ninth embodiment;

FIG. 19 is a diagram illustrating a lens configuration of an imaginglens according to a tenth embodiment;

FIG. 20 is a diagram illustrating spherical aberration, astigmatism anddistortion of a value example obtained by applying specific values tothe tenth embodiment;

FIG. 21 is a perspective view illustrating a mobile phone in a closedstate to which an imaging apparatus according to another embodiment ofthe present disclosure is applied, which will be more apparent incooperation with FIGS. 22 and 23;

FIG. 22 is a perspective view illustrating the mobile phone in an openstate; and

FIG. 23 is a block diagram thereof.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments for an imaging lens and an imagingapparatus of the present disclosure will be described.

[Configuration of Imaging Lens]

The imaging lens according to the embodiment of the present disclosureincludes an aperture stop, a first lens having a positive refractivepower, a second lens having a negative refractive power which is formedin a concave shape on both sides thereof, a third lens having a positiverefractive power which is formed in a meniscus shape in which a concavesurface is directed toward the side of an object, and a fourth lenshaving a negative refractive power in which a convex surface is directedtoward the object side, which are sequentially disposed from the objectside to the image side.

Accordingly, the positive, negative, positive and negative refractivepowers are disposed in the imaging lens, to form an arrangementconfiguration in which the positive refractive power proceeds.

By forming the second lens in the concave shape on both sides, totalreflection ghosting due to off-axis light beams diffuses in a peripheralportion of the lens, so that the ghosting light is prevented from beingincident to an imaging device such as a CCD or CMOS, which is effectivein correction of coma aberration.

Forming the third lens in the meniscus shape having the positiverefractive power is effective in aberration correction, andparticularly, is effective in field curvature and astigmatismcorrection.

By forming the fourth lens having the negative refractive power in theshape of which the convex surface is directed toward the object side,ghosting light which enters a peripheral portion of the fourth lens isprevented from being incident to the imaging device such as a CCD orCMOS by being reflected from the surface thereof on the object side.

Further, the imaging lens according to the embodiment of the presentdisclosure satisfies the following conditional expressions (1), (2),(3), (4) and (5).

0.40<f1/|f2|<0.80  (1)

0.80<|f2|/f3<1.50  (2)

0.90<f/|f4|<2.00  (3)

2.60<|(R2−R3)/f1|<4.00  (4)

νd1−νd2>25  (5)

Here, f1 is the focal length of the first lens, f2 is the focal lengthof the second lens, f3 is the focal length of the third lens, f4 is thefocal length of the fourth lens, f is the focal length of an entire lenssystem, R2 is a paraxial curvature radius of a surface on the objectside of the first lens, R3 is a paraxial curvature radius of a surfaceon the image side of the first lens, νd1 is the Abbe number of the firstlens, and νd2 is the Abbe number of the second lens.

The conditional expression (1) is a conditional expression relating toan appropriate refractive power distribution of the second lens in therefractive power of the first lens. The reason why the absolute value isused in the focal length of the second lens is because the second lenshas the negative refractive power. By setting the first lens and thesecond lens to have the refractive power arrangement shown in theconditional expression (1), it is possible to obtain an excellentaberration correction effect.

If f1/|f2| is beyond the upper limit of the conditional expression (1),the refractive power of the second lens becomes excessively strong, andit is thus difficult to correct off-axis aberration, and particularly tocorrect astigmatism and field curvature, which consequently lowersassembly efficiency at the time of manufacturing.

On the other hand, if f1/|f2| is beyond the lower limit of theconditional expression (1), the refractive power of the second lensbecomes excessively weak, and it is thus disadvantageous in terms ofreduction of the total optical length, which is disadvantageous in termsof miniaturization. Further, it is disadvantageous in terms ofcorrection of chromatic aberration, which makes it difficult to securean excellent optical performance suitable for an imaging device of ahigh pixel density.

For this reason, the imaging lens satisfies the conditional expression(1), and thus, it is possible to achieve miniaturization and to securean excellent optical performance suitable for an imaging device of ahigh pixel density.

The conditional expression (2) is a conditional expression relating toan appropriate refractive power distribution of the third lens in therefractive power of the second lens. The reason why the absolute valueis used in the focal length of the second lens is because the secondlens has the negative refractive power.

If |f2|/f3 is beyond the upper limit of the conditional expression (2),the refractive power of the third lens becomes excessively strong, andit is thus difficult to correct off-axis aberration, and particularly tocorrect astigmatism and field curvature, which consequently lowersassembly efficiency at the time of manufacturing.

On the other hand, if |f2|/f3 is beyond the lower limit of theconditional expression (2), the refractive power of the third lensbecomes excessively weak, and it is thus disadvantageous in terms ofreduction of the total optical length, which is disadvantageous in termsof miniaturization.

For this reason, the imaging lens satisfies the conditional expression(2), and thus, it is possible to achieve miniaturization and to securean excellent aberration correction performance to thereby secure anexcellent optical performance.

The conditional expression (3) is a conditional expression relating toan appropriate refractive power distribution of the fourth lens in therefractive powers of the lenses of the entire system. The reason why theabsolute value is used in the focal length of the fourth lens is becausethe fourth lens has the negative refractive power.

If f/|f4| is beyond the upper limit of the conditional expression (3),the refractive power of the fourth lens becomes excessively strong, andit is thus difficult to correct off-axis aberration, and particularly tocorrect field curvature and distortion, which consequently lowersassembly efficiency at the time of manufacturing.

On the other hand, if f/|f4| is beyond the lower limit of theconditional expression (3), the refractive power of the fourth lensbecomes excessively weak, and it is thus disadvantageous in terms ofreduction of the total optical length, which results in deterioration ofminiaturization.

For this reason, the imaging lens satisfies the conditional expression(3), and thus, it is possible to achieve miniaturization and to securean excellent aberration correction performance to thereby secure anexcellent optical performance.

The conditional expression (4) is a conditional expression relating tothe respective paraxial curvature radii of the surface on the objectside of the first lens and of the surface of the image side of the firstlens, and the refractive power of the first lens.

If |(R2−R3)/f1| is beyond the upper limit of the conditional expression(4), the refractive power of the first lens becomes excessively weak,and it is thus disadvantageous in terms of reduction of the totaloptical length, which is disadvantageous in terms of miniaturization.

On the other hand, if |(R2−R3)/f1| is beyond the lower limit of theconditional expression (4), the paraxial curvature radius differencebetween the surface on the object side of the first lens and the surfaceof the image side thereof becomes excessively small, and it is thusdifficult to correct aberration, and particularly to correct sphericalaberration and coma aberration through the lenses disposed on the imageside with reference to the first lens.

For this reason, the imaging lens satisfies the conditional expression(4), and thus, it is possible to achieve miniaturization and to securean excellent aberration correction performance to thereby secure anexcellent optical performance.

The conditional expression (5) is a conditional expression forregulating Abbe numbers in the short wavelength of the d-line of thefirst lens and the second lens.

By using a glass material in which the Abbe number is in the range ofthe conditional expression (5) as the first lens and the second lens, itis possible to perform an excellent chromatic aberration correction.Further, it is possible to suppress occurrence of peripheral comaaberration and field curvature.

As described above, since the imaging lens according to the embodimentof the present disclosure satisfies the conditional expressions (1),(2), (3), (4) and (5), the distribution of the focal lengths of thefirst lens having the positive refractive power, the second lens havingthe negative refractive power, the third lens having the positiverefractive power and the fourth lens having the negative refractivepower is appropriately performed.

Accordingly, it is possible to realize an imaging lens in which axialchromatic aberration, spherical aberration and field curvature arereliably corrected, whose total optical length is reduced, and whichachieves an excellent optical performance.

Specifically, it is possible to realize an imaging lens in which thefocal length is 26 mm to 35 mm in the 35 mm version, the value of theF-number is 2.1 to 2.6, and a total optical length with respect to adiagonal length (length from the center of the imaging device to anopposing angle) of the imaging device is 1.4 to 2.0.

As described above, since the value of the F-number is 2.1 to 2.6, thefocal length in the 35 mm version is 26 mm to 35 mm, and the totaloptical length with respect to the diagonal length of the imaging deviceis 1.4 to 2.0, it is possible to reduce the total optical length and torealize a bright optical system.

It is preferable that the imaging lens according to the embodiment ofthe present disclosure satisfy the following conditional expression (6).

0.30<|(R6−R7)/f3|<1.50  (6)

Here, R6 is a paraxial curvature radius of the surface on the objectside of the third lens, and R7 is a paraxial curvature radius of thesurface on the image side of the third lens.

The conditional expression (6) is a conditional expression relating tothe paraxial curvature radius of the surface on the object side of thethird lens, the paraxial curvature radius of the surface on the imageside of the third lens, and the refractive power of the third lens.

If |(R6−R7)/f3| is beyond the upper limit of the conditional expression(6), the paraxial curvature radius on the object side of the third lensis excessively large, and it is thus difficult to correct off-axisaberration. Further, a paraxial curvature radius difference between thesurface on the object side of the third lens and the surface on theimage side thereof is increased, which significantly lowersmanufacturing efficiency of the lens.

On the other hand, if |(R6−R7)/f3| is beyond the lower limit of theconditional expression (6), the paraxial curvature radius differencebetween the surface on the object side of the third lens and the surfaceon the image side thereof is increased, which significantly lowersmanufacturing efficiency of the lens.

For this reason, the imaging lens satisfies the conditional expression(6), and thus, it is possible to reliably correct off-axis aberration,and to achieve high manufacturing efficiency of the lens.

It is preferable that the value of the paraxial curvature radius (R6) onthe surface of the object side of the third lens be −7.054 mm to −3.335mm. Further, it is preferable that the value of the paraxial curvatureradius (R7) of the surface on the image side of the third lens be −1.983mm to −1.216 mm.

In the imaging lens according to the embodiment of the presentdisclosure, it is preferable to dispose the aperture stop between thetop of the surface on the object side of the first lens in the opticalaxis direction and an effective radius thereof.

In the imaging lens according to the embodiment of the presentdisclosure, a front-stop configuration is adopted, in which by settingthe position of the aperture stop in the range from the top of thesurface on the object side of the first lens in the optical axisdirection to the effective radius thereof, it is possible to increasethe amount of peripheral light, compared with a case where the aperturestop is disposed on the object side from the top of the surface of theobject side of the first lens. Further, it is possible to reduce thetotal optical length and to achieve miniaturization.

In the imaging lens according to the embodiment of the presentdisclosure, it is preferable to satisfy the following conditionalexpression (7).

3.00<|f4|/D8<7.00  (7)

Here, D8 is the central thickness of the fourth lens.

The conditional expression (7) is a conditional expression relating tothe refractive power of the fourth lens and the central thickness of thefourth lens.

If |f4|/D8 is beyond the upper limit of the conditional expression (7),the central thickness of the fourth lens becomes excessively thin, whichconsequently lowers manufacturing efficiency of the fourth lens.

On the other hand, if |f4|/D8 is beyond the lower limit of theconditional expression (7), the refractive power of the fourth lensbecomes excessively strong, and it is thus difficult to reliably correctaberration, and particularly to correct field curvature and distortion,which consequently lowers assembly efficiency at the time ofmanufacturing.

In the imaging lens according to the embodiment of the presentdisclosure, it is preferable to satisfy the following conditionalexpression (8).

1.00<R4/f2<30.00  (8)

Here, R4 is a paraxial curvature radius of the surface on the objectside of the second lens.

The conditional expression (8) is a conditional expression relating tothe paraxial curvature radius of the surface on the object side of thesecond lens and the refractive power of the second lens.

If R4/f2 is beyond the lower limit of the conditional expression (8),the paraxial curvature radius of the surface on the object side of thesecond lens becomes excessively small. Thus, the refractive power of thesecond lens becomes large, which consequently lowers manufacturingefficiency of the second lens.

On the other hand, if R4/f2 is beyond the upper limit of the conditionalexpression (8), the paraxial curvature radius of the surface on theobject side of the second lens becomes excessively large, ghosting lightgenerated in the peripheral portion of the lens enters the imagingdevice such as a CCD or CMOS, which causes deterioration of imagequality.

[Value Examples of Imaging Lens]

Hereinafter, specific embodiments of the imaging device of the presentdisclosure and value examples obtained by applying specific values tothe embodiments will be described with reference to the accompanyingdrawings and tables.

Meanings or the like of symbols shown in the following tables anddescription are as follows.

A “surface number Si” is an i-th surface counted from the object side tothe image side; a “paraxial curvature radius Ri” is a paraxial curvatureradius of the i-th surface; an “interval Di” is an axial surfaceinterval (the center thickness of the lens or air interval) between thei-th surface and an (i+1)-th surface; a “refractive index Ndi” is arefractive index in d-line (λ=587.6 nm) of a lens or the like startingfrom the i-th surface; and “νdi” is the Abbe number in d-line of thelens starting from the i-th surface.

An “STO” represents the aperture stop with respect to the “surfacenumber Si”, and “∞” represents a flat surface with respect to the“paraxial curvature radius Ri”.

“K” represents a conic constant, and “3rd” “4th”, . . . represent third,fourth, astigmatism coefficients, respectively.

In each table indicating the following astigmatism coefficients, “E-n”represents an exponential expression using “10” as the base, that is,“10^(−n)”. For example, “0.12345E-05” represents “0.12345×10⁻⁵”.

As the imaging lens used in each embodiment, there is an imaging lens inwhich a surface of a lens is formed in an aspherical shape. When thedepth of the aspherical surface is “Z”, the height from the optical axisis “Y”, the paraxial curvature radius is “R”, the conic constant is “K”,and the i-th aspherical coefficient (“i” is an integer of 3 or more) is“Ai”, the shape of the aspherical surface is defined by the followingexpression (1).

$\begin{matrix}{Z = {\frac{Y^{2}/R}{1 + \sqrt{1 - {\left( {1 + K} \right)\left( {Y/R} \right)^{2}}}} + {\sum\limits^{\;}{{Ai} \cdot Y^{i}}}}} & (1)\end{matrix}$

First Embodiment

FIG. 1 is a diagram illustrating a lens configuration of an imaging lens1 according to a first embodiment.

The imaging lens 1 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a first value example obtained by applying specific valuesto the imaging lens 1 according to the first embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 1.

TABLE 1 first value example lens data Si Ri Ndi νdi surface curvature Direfractive Abbe number radius interval index number  1 ∞ −0.220 — —(STO)  2 1.833 0.792 1.535 56.3  3 −8.067 0.030 — —  4 −26.471 0.5001.635 23.9  5 3.512 0.862 — —  6 −7.054 1.017 1.535 56.3  7 −1.696 0.100— —  8 3.056 0.700 1.535 56.3  9 1.038 0.350 — — 10 ∞ 0.150 1.518 64.111 ∞ 0.700 — — FNo = 2.2 f = 4.2 2ω = 69.8°

In the imaging lens 1, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the first value example are shown together with the conicconstants K, in Table 2.

TABLE 2 first value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 2.11E−01−2.26E−01 3 9.49E+00 4.21E−02 −1.01E−01 4 0.00E+00 9.32E−03 3.08E−02−2.44E−03 −4.35E−02 −2.22E−02 5 1.36E+00 1.13E−02 1.34E−02 1.89E−025.22E−04 4.38E−04 6 −2.98E+00 −1.93E−02 9.53E−02 −1.24E−01 1.24E−02−2.08E−03 7 −2.95E+00 −1.09E−01 1.39E−02 1.06E−01 −1.17E−01 2.35E−02 8−7.86E+00 −1.30E−01 −1.71E−01 9.90E−02 8.53E−03 4.55E−03 9 −3.72E+00−1.09E−02 −1.98E−01 1.61E−01 −3.66E−02 −6.02E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 1.79E−01 −6.63E−02 3 1.11E−01 −4.39E−024 7.79E−02 2.57E−02 −3.98E−02 5 1.56E−02 −2.81E−02 2.38E−02 6 2.12E−022.26E−03 −7.81E−03 7 −4.44E−03 1.25E−02 3.28E−03 −3.90E−03 8 −3.29E−03−1.73E−03 −7.11E−05 2.36E−04 9 1.56E−03 8.49E−04 −2.00E−04 —

FIG. 2 is a diagram illustrating spherical aberration, astigmatism anddistortion in the first value example.

In FIG. 2, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the first valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Second Embodiment

FIG. 3 is a diagram illustrating a lens configuration of an imaging lens2 according to a second embodiment.

The imaging lens 2 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a second value example obtained by applying specific valuesto the imaging lens 2 according to the second embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 3.

TABLE 3 second value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius interval index number  1 ∞ −0.160 — —(STO)  2 1.668 0.715 1.535 56.3  3 −6.610 0.030 — —  4 −21.536 0.4481.635 23.9  5 3.316 0.678 — —  6 −3.920 0.822 1.535 56.3  7 −1.689 0.251— —  8 2.846 0.626 1.535 56.3  9 1.110 0.350 — — 10 ∞ 0.100 1.518 64.111 ∞ 0.700 — — FNo = 2.4 f = 4.0 2ω = 72.6°

In the imaging lens 2, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the second value example are shown together with the conicconstants K, in Table 4.

TABLE 4 second value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 2.65E−01−3.39E−01 3 9.49E+00 3.35E−02 −1.33E−01 4 0.00E+00 1.23E−02 2.87E−023.66E−03 −5.35E−02 −2.95E−02 5 1.36E+00 5.77E−03 3.77E−02 2.61E−02−9.80E−03 −9.89E−03 6 2.05E+00 −3.97E−02 1.08E−01 −1.59E−01 2.14E−025.29E−03 7 −1.56E+00 −1.08E−01 2.01E−03 1.41E−01 −1.54E−01 3.83E−02 8−1.00+01 −1.46E−01 −1.88E−01 1.17E−01 8.13E−03 6.97E−03 9 −3.96E+00−7.27E−02 −1.55E−01 1.56E−01 −4.47E−02 −4.47E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 3.13E−01 −1.52E−01 3 1.72E−01 −7.65E−024 1.23E−01 4.36E−02 −5.94E−02 5 2.37E−02 −3.73E−02 5.87E−02 6 3.92E−02−9.56E−05 −2.76E−02 7 −6.02E−03 2.10E−02 5.42E−03 −8.08E−03 8 −4.41E−03−2.69E−03 −1.13E−04 3.92E−04 9 1.87E−03 1.26E−03 −3.65E−04

FIG. 4 is a diagram illustrating spherical aberration, astigmatism anddistortion of the second value example.

In FIG. 4, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the second valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Third Embodiment

FIG. 5 is a diagram illustrating a lens configuration of an imaging lens3 according to a third embodiment.

The imaging lens 3 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a third value example obtained by applying specific valuesto the imaging lens 3 according to the third embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 5.

TABLE 5 third value example lens data Si Ri Ndi νdi surface curvature Direfractive Abbe number radius interval index number  1 ∞ −0.124 — —(STO)  2 1.302 0.546 1.535 56.3  3 −5.350 0.023 — —  4 −21.416 0.3111.635 23.9  5 2.524 0.547 — —  6 −3.335 0.680 1.535 56.3  7 −1.319 0.199— —  8 1.962 0.466 1.535 56.3  9 0.809 0.272 — — 10 ∞ 0.080 1.518 64.111 ∞ 0.541 — — FNo = 2.4 f = 3.1 2ω = 73.4°

In the imaging lens 3, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the third value example are shown together with the conicconstants K, in Table 6.

TABLE 6 third value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 5.65E−01−1.20E+00 3 9.49E+00 7.30E−02 −4.70E−01 4 0.00E+00 2.21E−02 6.17E−024.82E−03 −1.92E−01 −1.30E−01 5 1.36E+00 1.31E−02 7.24E−02 6.88E−02−2.87E−02 −3.36E−02 6 3.39E+00 −5.47E−02 2.21E−01 −4.50E−01 7.23E−022.90E−02 7 −1.83E+00 −1.85E−01 3.15E−03 3.74E−01 −5.56E−01 1.70E−01 8−1.00E+01 −2.56E−01 −4.04E−01 3.23E−01 2.81E−02 3.15E−02 9 −3.81E+00−1.11E−01 −3.46E−01 4.40E−01 −1.58E−01 −2.23E−02 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 1.87E+00 −1.52E+00 — 3 1.01E+00−7.32E−01 — 4 7.33E−01 3.43E−01 −5.84E−01 — 5 1.48E−01 −2.86E−015.53E−01 — 6 2.40E−01 1.22E−02 −2.53E−01 — 7 −3.55E−02 1.61E−01 5.50E−02−1.00E−01 8 −2.62E−02 −2.04E−02 −1.07E−03 4.96E−03 9 1.06E−02 9.51E−03−3.49E−03 —

FIG. 6 is a diagram illustrating spherical aberration, astigmatism anddistortion of the third value example.

In FIG. 6, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the third valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Fourth Embodiment

FIG. 7 is a diagram illustrating a lens configuration of an imaging lens4 according to a fourth embodiment.

The imaging lens 4 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a fourth value example obtained by applying specific valuesto the imaging lens 4 according to the fourth embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 7.

TABLE 7 fourth value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius interval index number  1 ∞ −0.140 — —(STO)  2 1.702 0.744 1.535 56.3  3 −5.743 0.030 — —  4 −23.681 0.3711.635 23.9  5 3.178 0.671 — —  6 −5.033 0.918 1.535 56.3  7 −1.598 0.216— —  8 1.876 0.500 1.535 56.3  9 0.841 0.350 — — 10 ∞ 0.100 1.518 64.111 ∞ 0.700 — — FNo = 2.4 f = 3.8 2ω = 75.8°

In the imaging lens 4, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the fourth value example are shown together with the conicconstants K, in Table 8.

TABLE 8 fourth value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 2.56E−01−3.50E−01 3 9.49E+00 3.17E−02 −1.25E−01 4 0.00E+00 1.10E−02 3.74E−02−1.10E−02 −6.30E−02 −2.10E−02 5 1.36E+00 1.60E−02 2.43E−02 2.08E−02−6.73E−03 −3.60E−03 6 −1.00E+01 −3.09E−02 1.28E−01 −1.84E−01 9.09E−031.01E−02 7 −3.95E+00 −1.33E−01 5.34E−03 1.33E−01 −1.60E−01 3.74E−02 8−9.87E+00 −1.89E−01 −1.86E−01 1.20E−01 9.68E−03 7.61E−03 9 −3.77E+00−7.04E−02 −1.90E−01 1.80E−01 −4.49E−02 −6.36E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 3.57E−01 −1.92E−01 — 3 1.72E−01−7.66E−02 — 4 1.48E−01 5.82E−02 −8.63E−02 — 5 2.69E−02 −3.90E−025.46E−02 — 6 4.87E−02 4.97E−03 −3.03E−02 — 7 −4.66E−03 2.23E−02 5.82E−03−8.28E−03 8 −4.29E−03 −2.67E−03 −1.27E−04 3.64E−04 9 1.50E−03 1.25E−03−2.85E−04 —

FIG. 8 is a diagram illustrating spherical aberration, astigmatism anddistortion of the fourth value example.

In FIG. 8, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the fourth valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Fifth Embodiment

FIG. 9 is a diagram illustrating a lens configuration of an imaging lens5 according to a fifth embodiment.

The imaging lens 5 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a fifth value example obtained by applying specific valuesto the imaging lens 5 according to the fifth embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 9.

TABLE 9 fifth value example lens data Si Ri Ndi νdi surface curvature Direfractive Abbe number radius interval index number  1 ∞ −0.171 — —(STO)  2 1.829 0.767 1.535 56.3  3 −7.518 0.030 — —  4 −38.943 0.5011.635 23.9  5 3.362 0.817 — —  6 −5.650 0.865 1.535 56.3  7 −1.983 0.220— —  8 3.026 0.700 1.535 56.3  9 1.184 0.350 — — 10 ∞ 0.150 1.518 64.111 ∞ 0.700 — — FNo = 2.4 f = 4.3 2ω = 68.6°

In the imaging lens 5, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the fifth value example are shown together with the conicconstants K, in Table 10.

TABLE 10 fifth value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 2.12E−01−2.40E−01 3 9.49E+00 3.59E−02 −9.42E−02 4 0.00E+00 1.28E−02 2.24E−024.24E−04 −3.92E−02 −1.89E−02 5 1.36E+00 4.98E−03 2.59E−02 1.35E−02−7.45E−03 −1.17E−03 6 2.33E+00 −3.41E−02 8.86E−02 −1.10E−01 1.51E−02−3.28E−03 7 −2.82E+00 −1.17E−01 6.98E−03 1.05E−01 −1.12E−01 2.68E−02 8−1.00E+01 −1.25E−01 −1.74E−01 9.93E−02 8.63E−03 4.30E−03 9 −3.88E+00−2.53E−02 −1.78E−01 1.48E−01 −3.54E−02 −5.47E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 2.01E−01 −8.34E−02 3 1.09E−01 −4.57E−024 7.96E−02 2.53E−02 −4.05E−02 5 2.02E−02 −2.25E−02 2.36E−02 6 2.03E−021.51E−03 −8.52E−03 7 −3.42E−03 1.24E−02 2.85E−03 −4.32E−03 8 −3.40E−03−1.81E−03 −9.12E−05 2.33E−04 9 1.88E−03 8.17E−04 −2.44E−04

FIG. 10 is a diagram illustrating spherical aberration, astigmatism anddistortion of the fifth value example.

In FIG. 10, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the fifth valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Sixth Embodiment

FIG. 11 is a diagram illustrating a lens configuration of an imaginglens 6 according to a sixth embodiment.

The imaging lens 6 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a sixth value example obtained by applying specific valuesto the imaging lens 6 according to the sixth embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 11.

TABLE 11 sixth value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius interval index number  l ∞ −0.140 — —(STO)  2 1.422 0.618 1.535 56.3  3 −5.853 0.023 — —  4 −25.114 0.3881.635 23.9  5 2.576 0.602 — —  6 −5.305 0.775 1.535 56.3  7 −1.257 0.078— —  8 2.389 0.543 1.535 56.3  9 0.802 0.272 — — 10 ∞ 0.120 1.518 64.111 ∞ 0.543 — — FNo = 2.2 f = 3.2 2ω = 71.4°

In the imaging lens 6, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the sixth value example are shown together with the conicconstants K, in Table 12.

TABLE 12 sixth value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 4.47E−01−8.06E−01 3 9.49E+00 7.55E−02 −3.42E−01 4 0.00E+00 1.12E−02 5.57E−02−1.43E−02 −1.54E−01 −9.18E−02 5 1.36E+00 7.24E−03 3.67E−02 4.81E−02−1.49E−02 −1.21E−02 6 −1.00E+01 −3.98E−02 2.11E−01 −3.43E−01 3.49E−02−5.82E−03 7 −3.27E+00 −1.82E−01 2.57E−02 2.88E−01 −4.10E−01 1.12E−01 8−1.00E+01 −2.02E−01 −3.63E−01 2.73E−01 2.87E−02 2.00E−02 9 −4.35E+003.88E−02 −4.74E−01 4.57E−01 −1.28E−01 −2.82E−02 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 1.09E+00 −7.10E−01 3 6.63E−01 −4.43E−014 4.74E−01 2.08E−01 −3.97E−01 5 9.04E−02 −1.94E−01 2.50E−01 6 1.31E−011.56E−02 −9.09E−02 7 −2.40E−02 9.46E−02 3.10E−02 −5.04E−02 8 −1.90E−02−1.31E−02 −4.64E−04 2.87E−03 9 8.82E−03 6.72E−03 −2.00E−03

FIG. 12 is a diagram illustrating spherical aberration, astigmatism anddistortion of the sixth value example.

In FIG. 12, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the sixth valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Seventh Embodiment

FIG. 13 is a diagram illustrating a lens configuration of an imaginglens 7 according to a seventh embodiment.

The imaging lens 7 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a seventh value example obtained by applying specificvalues to the imaging lens 7 according to the seventh embodiment isshown together with an F-number “FNo”, the focal length “f” of an entirelens system and a field angle “2ω”, in Table 13.

TABLE 13 seventh value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius Interval index number  1 ∞ −0.154 — —(STO)  2 1.855 0.723 1.535 56.3  3 −6.475 0.038 — —  4 −50.724 0.5971.640 23.3  5 3.319 0.806 — —  6 −4.834 0.918 1.535 56.3  7 −1.566 0.176— —  8 3.354 0.630 1.535 56.3  9 0.986 0.362 — — 10 ∞ 0.100 1.518 64.111 ∞ 0.650 — — FNo = 2.4 f = 4.3 2ω = 68.8°

In the imaging lens 7, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the seventh value example are shown together with the conicconstants K, in Table 14.

TABLE 14 seventh value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 1.96E−01−2.35E−01 3 9.49E+00 3.20E−02 −8.95E−02 4 0.00E+00 1.15E−02 3.10E−02−1.19E−03 −3.66E−02 −1.51E−02 5 1.36E+00 −4.29E−04 3.71E−02 1.49E−02−9.42E−03 −6.09E−03 6 5.53E+00 −2.26E−02 9.46E−02 −1.19E−01 1.54E−033.45E−03 7 −7.23E+00 −1.62E−01 3.48E−03 9.90E−02 −9.37E−02 2.16E−02 8−8.33E+00 −1.98E−01 −1.20E−01 9.13E−02 5.99E−03 3.43E−03 9 −4.52E+00−4.33E−02 −1.32E−01 1.14E−01 −2.78E−02 −3.34E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 1.90E−01 −8.20E−02 — 3 9.70E−02−4.00E−02 — 4 7.19E−02 2.58E−02 −3.57E−02 — 5 1.25E−02 −1.62E−022.90E−02 — 6 2.69E−02 2.96E−03 −1.69E−02 — 7 −3.78E−03 9.40E−03 2.17E−03−3.04E−03 8 −2.80E−03 −1.48E−03 −7.90E−05 2.04E−04 9 8.50E−03 6.44E−04−1.51E−04 —

FIG. 14 is a diagram illustrating spherical aberration, astigmatism anddistortion of the seventh value example.

In FIG. 14, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the seventh valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Eighth Embodiment

FIG. 15 is a diagram illustrating a lens configuration of an imaginglens 8 according to an eighth embodiment.

The imaging lens 8 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of an eighth value example obtained by applying specificvalues to the imaging lens 8 according to the eighth embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 15.

TABLE 15 eighth value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius interval index number  1 ∞ −0.180 — —(STO)  2 1.843 0.797 1.535 56.3  3 −6.073 0.030 — —  4 −12.987 0.4921.635 23.9  5 4.097 0.822 — —  6 −5.424 0.906 1.535 56.3  7 −1.549 0.123— —  8 2.862 0.630 1.535 56.3  9 0.938 0.350 — — 10 ∞ 0.150 1.518 64.111 ∞ 0.700 — — FNo = 2.4 f = 4.1 2ω = 70.9°

In the imaging lens 8, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the eighth value example are shown together with the conicconstants K, in Table 16.

TABLE 16 eighth value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 2.02E−01−2.29E−01 3 9.49E+00 2.81E−02 −1.05E−01 4 0.00E+00 1.39E−02 2.56E−02−9.45E−03 −4.38E−02 −1.64E−02 5 1.36E+00 1.63E−02 1.52E−02 1.64E−02−2.22E−03 1.92E−03 6 4.07E+00 −1.23E−02 9.80E−02 −1.33E−01 5.37E−03−1.01E−03 7 −4.76E+00 −1.00E−01 −7.56E−03 9.70E−02 −1.14E−01 2.59E−02 8−1.00E+01 −1.57E−01 −1.59E−01 1.01E−01 7.96E−03 4.07E−03 9 −3.93E+00−4.87E−02 −1.68E−01 1.54E−01 −3.69E−02 −6.08E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 1.86E−01 −8.23E−02 — 3 1.06E−01−3.94E−02 — 4 8.53E−02 2.96E−02 −4.31E−02 — 5 1.97E−02 −2.38E−022.22E−02 — 6 2.45E−02 3.06E−03 −1.12E−02 — 7 −3.78E−03 1.25E−02 3.26E−03−3.87E−03 8 −3.32E−03 −1.76E−03 −3.91E−05 2.37E−04 9 1.57E−03 8.92E−04−2.12E−04 —

FIG. 16 is a diagram illustrating spherical aberration, astigmatism anddistortion of the eighth value example.

In FIG. 16, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the value example 8,various aberrations are reliably corrected and an excellent imagingperformance is achieved.

Ninth Embodiment

FIG. 17 is a diagram illustrating a lens configuration of an imaginglens 9 according to a ninth embodiment.

The imaging lens 9 includes an aperture stop STO, a first lens G1 havinga positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a ninth value example obtained by applying specific valuesto the imaging lens 9 according to the ninth embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 17.

TABLE 17 ninth value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius interval index number  1 ∞ −0.160 — —(STO)  2 1.835 0.763 1.535 56.3  3 −5.223 0.030 — —  4 −8.082 0.4301.614 25.6  5 4.013 0.931 — —  6 −5.185 0.894 1.535 56.3  7 −1.849 0.100— —  8 1.599 0.650 1.535 56.3  9 0.772 0.382 — — 10 ∞ 0.100 1.518 64.111 ∞ 0.700 — — FNo = 2.4 f = 4.1 2ω = 71.3°

In the imaging lens 9, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the ninth value example are shown together with the conicconstants K, in Table 18.

TABLE 18 ninth value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 2.12E−01−2.52E−01 3 9.49E+00 5.13E−02 −8.63E−02 4 0.00E+00 1.75E−02 3.55E−02−9.14E−03 −4.21E−02 −3.26E−02 5 1.36E+00 1.03E−02 2.46E−02 2.86E−02−1.53E−02 −9.77E−03 6 1.94E+00 3.70E−02 8.15E−02 −1.33E−01 2.50E−02−1.62E−02 7 −1.77E−01 −2.28E−02 −5.38E−02 1.70E−01 −1.37E−01 3.47E−02 8−4.66E+00 −1.67E−01 −2.15E−01 1.13E−01 1.44E−02 8.84E−03 9 −3.21E+00−1.05E−01 −1.13E−01 1.27E−01 −3.14E−02 −5.24E−03 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 2.21E−01 −9.89E−02 — 3 9.51E−02−4.08E−02 — 4 9.92E−02 1.62E−02 −3.89E−02 — 5 3.53E−02 −2.75E−022.22E−02 — 6 2.38E−02 5.09E−03 −8.84E−03 — 7 −1.49E−02 1.49E−02 5.01E−03−4.28E−03 8 −4.10E−03 −2.92E−03 −9.40E−05 3.47E−04 9 1.17E−03 9.10E−04−2.05E−04 —

FIG. 18 is a diagram illustrating spherical aberration, astigmatism anddistortion of the ninth value example.

In FIG. 18, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the ninth valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

Tenth Embodiment

FIG. 19 is a diagram illustrating a lens configuration of an imaginglens 10 according to a tenth embodiment.

The imaging lens 10 includes an aperture stop STO, a first lens G1having a positive refractive power, a second lens G2 having a negativerefractive power, a third lens G3 having a positive refractive power,and a fourth lens G4 having a negative refractive power, which aresequentially disposed from the side of an object to the image side.

The first lens G1 is formed in a convex shape on both sides thereof.

The second lens G2 is formed in a concave shape on both sides thereof,and the absolute value of the paraxial curvature radius of the surfacethereof on the image side is smaller than the absolute value of theparaxial curvature radius of the surface thereof on the object side.

The third lens G3 is formed in a meniscus shape in which a concavesurface is directed toward the object side.

The fourth lens G4 is formed in a shape in which a surface in theproximity of the optical axis forms a convex surface toward the objectside, and has an inflection point in the effective diameter of thesurface on the object side and in the effective diameter of the surfaceon the image side, respectively.

A seal glass SG is disposed between the fourth lens G4 and an imagesurface IMG.

Lens data of a tenth value example obtained by applying specific valuesto the imaging lens 10 according to the tenth embodiment is showntogether with an F-number “FNo”, the focal length “f” of an entire lenssystem and a field angle “2ω”, in Table 19.

TABLE 19 tenth value example lens data Si Ri Ndi νdi surface curvatureDi refractive Abbe number radius interval index number  1 ∞ −0.120 — —(STO)  2 1.441 0.562 1.535 56.3  3 −5.027 0.030 — —  4 −39.382 0.4631.614 25.6  5 2.577 0.626 — —  6 −3.753 0.713 1.535 56.3  7 −1.216 0.137— —  8 2.604 0.489 1.535 56.3  9 0.765 0.281 — — 10 ∞ 0.080 1.518 64.111 ∞ 0.505 — — FNo = 2.4 f = 3.3 2ω = 68.9°

In the imaging lens 10, both surfaces (the second surface and the thirdsurface) of the first lens G1, both surfaces (the fourth surface and thefifth surface) of the second lens G2, both surfaces (the sixth surfaceand the seventh surface) of the third lens G3, and both surfaces (theeighth surface and the ninth surface) of the fourth lens G4 are formedas aspherical surfaces. The aspherical coefficients of the asphericalsurfaces in the tenth value example are shown together with the conicconstants K, in Table 20.

TABLE 20 first value example aspherical data Si K surface conic numberconstant 3rd 4th 5th 6th 7th 1 — — — — — — (STO) 2 −1.12E+01 4.18E−01−8.33E−01 3 9.49E+00 6.84E−02 −3.17E−01 4 0.00E+00 1.90E−02 6.62E−023.26E−03 −1.30E−01 −6.89E−02 5 1.36E+00 −7.12E−04 7.93E−02 4.11E−02−3.34E−02 −2.78E−02 6 5.53E+00 −3.75E−02 2.02E−01 −3.27E−01 5.46E−031.57E−02 7 −7.23E+00 −2.68E−01 7.43E−03 2.72E−01 −3.32E−01 9.86E−02 8−8.33E+00 −3.29E−01 −2.57E−01 2.51E−01 2.12E−02 1.57E−02 9 −4.52E+00−7.19E−02 −2.83E−01 3.15E−01 −9.86E−02 −1.53E−02 Si surface number 8th9th 10th 11th 1 — — — — (STO) 2 1.12E+00 −8.00E−01 3 5.70E−01 −3.90E−014 4.22E−01 1.95E−01 −3.49E−01 5 7.34E−02 −1.23E−01 2.83E−01 6 1.58E−012.24E−02 −1.65E−01 7 −2.23E−02 7.12E−02 2.12E−02 −3.82E−02 8 −1.65E−02−1.12E−02 −7.70E−04 2.56E−03 9 5.00E−03 4.88E−03 −1.47E−03

FIG. 20 is a diagram illustrating spherical aberration, astigmatism anddistortion of the tenth value example.

In FIG. 20, in the spherical aberration figure, the value of g-line (awavelength of 435.8400 nm) is indicated by a two-dot chain line, thevalue of d-line (a wavelength of 587.5600 nm) is indicated by a solidline, and the value of c-line (a wavelength of 656.2700 nm) is indicatedby a dotted line, respectively. In the astigmatism figure, the value ona sagittal image surface is indicated by a solid line, and the value ona meridional image surface is indicated by a dotted line.

It is obvious from each aberration figure that in the tenth valueexample, various aberrations are reliably corrected and an excellentimaging performance is achieved.

[Respective Values in Conditional Expressions or the Like of ImagingLens]

Respective values of the conditional expressions (1) to (8) in theimaging lenses 1 to 10 are shown in Table 21 and Table 22.

TABLE 21 First Second Third Fourth Fifth Sixth Seventh Eighth NinthTenth value value value value value value value value value valueexample example example example example example example example exampleexample Focal length of entire lens 4.200 3.953 3.045 3.752 4.300 3.1314.300 4.108 4.106 4.200 system f Focal length of first lens f1 2.8622.558 2.008 2.534 2.821 2.193 2.770 2.730 2.640 2.160 Focal length ofsecond lens f2 −4.800 −4.447 −3.501 −4.343 −4.800 −3.612 −4.800 −4.800−4.308 −3.764 Focal length of third lens f3 3.899 4.896 3.635 3.9885.258 2.846 3.929 3.735 4.915 3.065 Focal length of fourth lens f4−3.334 −3.876 −2.986 −3.411 −4.175 −2.610 −2.867 −2.934 −3.844 −2.235Abbe number of first lens νd1 56.3 56.3 56.3 56.3 56.3 56.3 56.3 56.356.3 56.3 Abbe number of second lens νd2 23.9 23.9 23.9 23.9 23.9 23.923.2 23.9 25.6 25.6 Paraxial curvature radius of 1.833 1.668 1.302 1.7021.829 1.419 1.855 1.843 1.835 1.441 surface on object side of first lensR2 Paraxial curvature radius of −8.067 −6.610 −5.350 −5.743 −7.518−5.880 −6.475 −6.073 −5.223 −5.027 surface on image side of first lensR3 Paraxial curvature radius of −7.054 −3.920 −3.335 −5.033 −5.650−5.174 −4.834 −5.424 −5.185 −3.753 surface on object side of third lensR6 Paraxial curvature radius of −1.696 −1.689 −1.319 −1.598 −1.983−1.244 −1.566 −1.549 −1.849 −1.216 surface on image side of third lensR7 Center thickness of fourth lens 0.700 0.626 0.466 0.500 0.700 0.5430.630 0.630 0.650 0.489 D8 Paraxial curvature radius of −26.471 −21.536−21.416 −23.681 −38.943 −28.782 −50.724 −12.987 −8.082 −39.382 surfaceon object side of second lens R4

TABLE 22 First Second Third Fourth Fifth Sixth Seventh Eighth NinthTenth value value value value value value value value value valueexample example example example example example example example exampleexample (1) 0.40 < f1/|f2| < 0.80 0.596 0.575 0.573 0.583 0.588 0.6070.577 0.569 0.613 0.574 (2) 0.40 < f1/|f2| < 0.80 1.231 0.908 0.9631.089 0.913 1.269 1.222 1.285 0.876 1.228 (3) 0.90 < f/|f4| < 2.00 1.2601.020 1.020 1.100 1.030 1.200 1.500 1.400 1.068 1.879 (4) 2.60 < |(R2 −R3)/f1| < 4.00 3.459 3.236 3.313 2.938 3.314 3.328 3.007 2.900 2.6742.995 (5) νd1 − νd2 > 25 32.4 32.4 32.4 32.4 32.4 32.4 33.1 32.4 30.730.7 (6) 0.30 < |(R6 − R7)/f3| < 1.50 1.374 0.456 0.555 0.861 0.6971.381 0.832 1.038 0.679 0.828 (7) 3.00 < |f4|/D8 < 7.00 4.762 6.1876.409 6/823 5.964 4.801 4.550 4.658 5.914 4.569 (8) 1.00 < R4/f2 < 30.005.515 4.843 6.118 5.452 8.113 7.968 10.567 2.706 1.876 10.464

As is obvious from Table 22, the imaging lenses 1 to 10 satisfy theconditional expressions (1) to (8).

Further, focal lengths of the imaging lenses 1 to 10 in the 35 mmversion, values of the F-number, and ratios of a total optical length toa diagonal length (length from the center of the imaging device to anopposing angle) of the imaging device are shown in Table 23.

TABLE 23 First Second Third Fourth Fifth Sixth Seventh Eighth NinthTenth value value value value value value value value value valueexample example example example example example example example exampleexample Focal length in 30 28 28 27 31 29 31 30 30 31 35 mm version (mm)FNo 2.2 2.4 2.4 2.4 2.4 2.2 2.4 2.4 2.4 2.4 Total optical length/ 1.71.6 1.6 1.5 1.7 1.7 1.7 1.7 1.7 1.7 Sensor opposing angle

As shown in Table 23, in the imaging lenses 1 to 10, the focal lengthsare 27 mm to 31 mm in the 35 mm version, the value of the F-number is2.2 to 2.4, and the ratios of the total optical length to the diagonallength of the imaging device are 1.5 to 1.7.

[Configuration of Imaging Apparatus]

The imaging apparatus according to the embodiment of the presentdisclosure includes an imaging lens and an imaging device which convertsan optical image formed by the imaging lens into an electric signal. Theimaging lens includes an aperture stop, a first lens having a positiverefractive power, a second lens having a negative refractive power whichis formed in a concave shape on both sides thereof, a third lens havinga positive refractive power which is formed in a meniscus shape in whicha concave surface is directed toward the side of an object, and a fourthlens having a negative refractive power in which a convex surface isdirected toward the object side, which are sequentially disposed fromthe object side to the image side.

Accordingly, in the imaging apparatus according to the embodiment of thepresent disclosure, the positive, negative, positive and negativerefractive powers are disposed in the imaging lens, to form anarrangement configuration in which the positive refractive powerproceeds.

By forming the second lens in the concave shape on both sides, totalreflection ghosting due to off-axis light beams diffuses in a peripheralportion of the lens, so that the ghosting light is prevented from beingincident to an imaging device such as a CCD or CMOS, which is effectivein correction of coma aberration.

Forming the third lens in the meniscus shape having the positiverefractive power is effective in aberration correction, andparticularly, is effective in field curvature and astigmatism.

By forming the fourth lens having the negative refractive power in theshape of which the convex surface is directed toward the object side,ghosting light which enters a peripheral portion of the fourth lens isprevented from being incident to the imaging device such as a CCD orCMOS by being reflected from the surface thereof on the object side.

Further, the imaging lens according to the embodiment of the presentdisclosure satisfies the following conditional expressions (1), (2),(3), (4) and (5).

0.40<|f1/|f2<0.80  (1)

0.80<|f2|/f3<1.50  (2)

0.90<f/|f4|<2.00  (3)

2.60<|(R2−R3)/f1|<4.00  (4)

νd1−νd2>25  (5)

Here, f1 is the focal length of the first lens, f2 is the focal lengthof the second lens, f3 is the focal length of the third lens, f4 is thefocal length of the fourth lens, f is the focal length of an entire lenssystem, R2 is a paraxial curvature radius of a surface on the objectside of the first lens, R3 is a paraxial curvature radius of a surfaceon the image side of the first lens, νd1 is the Abbe number of the firstlens, and νd2 is the Abbe number of the second lens.

The conditional expression (1) is a conditional expression relating toan appropriate refractive power distribution of the second lens in therefractive power of the first lens. The reason why the absolute value isused in the focal length of the second lens is because the second lenshas the negative refractive power. By setting the first lens and thesecond lens to have the refractive power arrangement shown in theconditional expression (1), it is possible to obtain an excellentaberration correction effect.

If f1/|f2| is beyond the upper limit of the conditional expression (1),the refractive power of the second lens becomes excessively strong, andit is thus difficult to correct off-axis aberration, and particularly tocorrect astigmatism and field curvature, which consequently lowersassembly efficiency at the time of manufacturing.

On the other hand, if f1/|f2| is beyond the lower limit of theconditional expression (1), the refractive power of the second lensbecomes excessively weak, and it is thus disadvantageous in reduction ofthe total optical length, which is disadvantageous in miniaturization.Further, it is disadvantageous in correction of chromatic aberration,which makes it difficult to secure an excellent optical performancesuitable for an imaging device of a high pixel density.

For this reason, the imaging lens satisfies the conditional expression(1), and thus, it is possible for the imaging apparatus to achieveminiaturization and to secure an excellent optical performance suitablefor an imaging device of a high pixel density.

The conditional expression (2) is a conditional expression relating toan appropriate refractive power distribution of the third lens in therefractive power of the second lens. The reason why the absolute valueis used in the focal length of the second lens is because the secondlens has the negative refractive power.

If |f2|/f3 is beyond the upper limit of the conditional expression (2),the refractive power of the third lens becomes excessively strong, andit is thus difficult to correct off-axis aberration, and particularly tocorrect astigmatism and field curvature, which consequently lowersassembly efficiency at the time of manufacturing.

On the other hand, if |f2|/f3 is beyond the lower limit of theconditional expression (2), the refractive power of the third lensbecomes excessively weak, and it is thus disadvantageous in terms ofreduction of the total optical length, which is disadvantageous in termsof miniaturization.

For this reason, the imaging lens satisfies the conditional expression(2), and thus, it is possible for the imaging apparatus to achieveminiaturization and to secure an excellent aberration correctionperformance to thereby secure an excellent optical performance.

The conditional expression (3) is a conditional expression relating toan appropriate refractive power distribution of the fourth lens in therefractive powers of the lenses of the entire system. The reason why theabsolute value is used in the focal length of the fourth lens is becausethe fourth lens has the negative refractive power.

If f/|f4| is beyond the upper limit of the conditional expression (3),the refractive power of the fourth lens becomes excessively strong, andit is thus difficult to correct off-axis aberration, and particularly tocorrect field curvature and distortion, which consequently lowersassembly efficiency at the time of manufacturing.

On the other hand, if f/|f4| is beyond the lower limit of theconditional expression (3), the refractive power of the fourth lensbecomes excessively weak, and it is thus disadvantageous in terms ofreduction of the total optical length, which results in deterioration ofminiaturization.

For this reason, the imaging lens satisfies the conditional expression(3), and thus, it is possible for the imaging apparatus to achieveminiaturization and to secure an excellent aberration correctionperformance to thereby secure an excellent optical performance.

The conditional expression (4) is a conditional expression relating tothe respective paraxial curvature radii of the surface on the objectside of the first lens and of the surface of the image side of the firstlens, and the refractive power of the first lens.

If |(R2−R3)/f1| is beyond the upper limit of the conditional expression(4), the refractive power of the first lens becomes excessively weak,and it is thus disadvantageous in terms of reduction of the totaloptical length, which is disadvantageous in terms of miniaturization.

On the other hand, if |(R2−R3)/f1| is beyond the lower limit of theconditional expression (4), the paraxial curvature radius differencebetween the surface on the object side of the first lens and the surfaceof the image side thereof becomes excessively small, and it is thusdifficult to correct aberration, and particularly to correct sphericalaberration and coma aberration through the lenses disposed on the imageside from the first lens.

For this reason, the imaging apparatus satisfies the conditionalexpression (4), and thus, it is possible to achieve miniaturization andto secure an excellent aberration correction performance to therebysecure an excellent optical performance.

The conditional expression (5) is a conditional expression forregulating Abbe numbers in short wavelength of d-line of the first lensand the second lens.

By using a glass material in which the Abbe number is in the range ofthe conditional expression (5) as the first lens and the second lens, itis possible to perform an excellent chromatic aberration correction.Further, it is possible to suppress occurrence of peripheral comaaberration and field curvature.

As described above, since the imaging lens according to the embodimentof the present disclosure satisfies the conditional expressions (1),(2), (3), (4) and (5), the distribution of the focal lengths of thefirst lens having the positive refractive power, the second lens havingthe negative refractive power, the third lens having the positiverefractive power and the fourth lens having the negative refractivepower is appropriately performed.

Accordingly, it is possible to realize an imaging apparatus whichincludes an imaging lens in which axial chromatic aberration, sphericalaberration and field curvature are reliably corrected, whose totaloptical length is reduced, and which achieves an excellent opticalperformance.

Specifically, it is possible to realize an imaging apparatus whichincludes an imaging lens in which focal lengths are 26 mm to 35 mm inthe 35 mm version, values of the F-number are 2.1 to 2.6, and ratios ofa total optical length to a diagonal length (length from the center ofthe imaging device to an opposing angle) of the imaging device are 1.4to 2.0.

As described above, since the values of the F-number are 2.1 to 2.6, thefocal lengths in the 35 mm version are 26 mm to 35 mm, and the ratios ofthe total optical length to the diagonal length of the imaging deviceare 1.4 to 2.0, it is possible to reduce the total optical length and torealize a bright optical system.

[One Embodiment of Imaging Apparatus]

Next, an embodiment of the present disclosure in which the imagingapparatus of the present disclosure is applied to a mobile phone will bedescribed (see FIGS. 21 to 23).

As shown in FIGS. 21 and 22, in a mobile phone 10, a display section 20and a main body 30 are foldably connected by a hinge section 40. Thedisplay section 20 and the main body 30 are in a folded state whencarried, as shown in FIG. 21. The display section 20 and the main body30 are in an opened state when used, for example, during communication,as shown in FIG. 22.

A liquid crystal display panel 21 is disposed on one surface of thedisplay section 20, and a speaker 22 is installed above the liquidcrystal display panel 21. In the display section 20 are assembled animaging unit 100 which includes an imaging lens 1, an imaging lens 2, animaging lens 3, an imaging lens 4, an imaging lens 5, an imaging lens 6,an imaging lens 7, an imaging lens 8, an imaging lens 9 or an imaginglens 10. An infrared communication section 23 for performingcommunication through infrared light is installed in the display section20.

A cover lens 24 which is positioned on the side of an object of a firstlens G1 of the imaging unit 100 is disposed on the other surface of thedisplay section 20.

A variety of operation keys 31, 31, . . . such as a numeric key and apower key are installed on one surface of the main body 30. Further, amicrophone 32 is installed on one surface of the main body 30. A memorycard slot 33 is formed on a side surface of the main body 30, and amemory card 40 is inserted into or detached from the memory card slot33.

FIG. 23 is a block diagram illustrating a configuration of the mobilephone 10.

The mobile phone 10 includes a CPU (Central Processing Unit) 50, whichcontrols an overall operation of the mobile phone 10. For example, inthe CPU 50, a control program stored in a ROM (Read Only Memory) 51 isexpanded in a RAM (Random Access Memory) 52, and the operation of themobile phone 10 is controlled through a bus 53.

A camera control section 60 has a function of controlling the imagingunit 100 to image a still image or a moving image. The camera controlsection 60 compresses image information obtained by photographing asaccording to JPEG (Joint Photographic Expert Group), MPEG (MovingPicture Expert Group) or the like, and transmits the compressed data tothe bus 53. The imaging unit 100 includes an imaging device 101 such asa CCD (Charge Coupled Device) or CMOS (Complementary Metal OxideSemiconductor), in addition to the imaging lens 1, the imaging lens 2,the imaging lens 3, the imaging lens 4, the imaging lens 5, the imaginglens 6, the imaging lens 7, the imaging lens 8, the imaging lens 9 orthe imaging lens 10.

The image information transmitted through the bus 53 is temporarilystored in the RAM 52, and is output to a memory card interface 41 asnecessary to be stored in the memory card 40 through the memory cardinterface 41 or to be displayed on the liquid crystal display panel 21through the display control section 54. Further, at the same time,during photographing, audio information which is recorded through themicrophone 32 is temporarily stored in the RAM 52 through an audio codec70 or is stored in the memory card 40, and is output from the speaker 22through the audio codec 70 at the same time when an image is displayedon the liquid crystal display panel 21.

The image information or audio information is output to an infraredlight interface 55 as necessary, is output outside through the infraredlight communicating section 23 by the infrared light interface 55, andis transmitted to a different apparatus including an infrared lightcommunicating section, for example, a mobile phone, a personal computer,a PDA (Personal Digital Assistance) or the like. When a moving image ora still image is displayed on the liquid crystal display panel 21 on thebasis of the image information stored in the RAM 52 or the memory card40, the camera control section 60 transmits image data obtained bydecoding or decompressing a file stored in the RAM 52 or the memory card40 to the display control section 54 through the bus 53.

A communication control section 80 performs transmission and receptionof radio waves between the communication control section 80 and a basestation through an antenna (not shown) installed in the display section20. In an audio communication mode, the communication control section 80processes the received audio information and outputs the result to thespeaker 22 through the audio codec 70. Further, the communicationcontrol section 80 receives audio collected by the microphone 32 throughthe audio codec 70 and performs a predetermined process for the audio tobe transmitted.

As described above, since it is possible to reduce the total opticallength in the imaging lens 1, the imaging lens 2, the imaging lens 3,the imaging lens 4, the imaging lens 5, the imaging lens 6, the imaginglens 7, the imaging lens 8, the imaging lens 9 and the imaging lens 10,it is possible to easily assemble the imaging lens into an imagingapparatus such as a mobile phone 10 in which a thin appearance isdesired.

In the above-described embodiments, the imaging apparatus is applied tothe mobile phone as an example, but the application range of the imagingapparatus is not limited to a mobile phone. That is, the imagingapparatus can be widely applied to a variety of digital input/outputdevices such as a digital video camera, a digital still camera, apersonal computer mounted with a camera or a PDA (Personal DigitalAssistant) mounted with a camera.

Any shapes and dimensions of the respective sections shown in theabove-described embodiments are only specific examples for implementingthe embodiments in practice, and thus should not be interpreted aslimiting the technical scope of the present disclosure.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2010-278528 filed in theJapan Patent Office on Dec. 14, 2010, the entire content of which ishereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. An imaging lens comprising: an aperture stop; a first lens having apositive refractive power; a second lens having a negative refractivepower which is formed in a concave shape on both sides thereof; a thirdlens having a positive refractive power which is formed in a meniscusshape in which a concave surface is directed toward the side of anobject; and a fourth lens having a negative refractive power in which aconvex surface is directed toward the object side, which aresequentially disposed from the object side to the image side, whereinthe imaging lens satisfies the following conditional expressions (1),(2), (3), (4) and (5):0.40<f1/|f2|<0.80  (1)0.80<<|f2/f3<1.50  (2)0.90<f/|f4|<2.00  (3)2.60<|(R2−R3)/f1|<4.00  (4)νd1−νd2>25  (5) where f1 is a focal length of the first lens, f2 is afocal length of the second lens, f3 is a focal length of the third lens,f4 is a focal length of the fourth lens, f is a focal length of anentire lens system, R2 is a paraxial curvature radius of a surface onthe object side of the first lens, R3 is a paraxial curvature radius ofa surface on the image side of the first lens, νd1 is an Abbe number ofthe first lens, and νd2 is an Abbe number of the second lens.
 2. Theimaging lens according to claim 1, wherein the imaging lens satisfiesthe following conditional expression (6):0.30<|(R6−R7)/f3|<1.50  (6) where R6 is a paraxial curvature radius ofthe surface on the object side of the third lens, and R7 is a paraxialcurvature radius of a surface on the image side of the third lens. 3.The imaging lens according to claim 1, wherein the aperture stop isdisposed between the top of the surface on the object side of the firstlens and an effective diameter thereof.
 4. The imaging lens according toclaim 1, wherein the imaging lens satisfies the following conditionalexpression (7):3.00<|f4|/D8<7.00  (7) where D8 is a center thickness of the fourthlens.
 5. The imaging lens according to claim 1, wherein the imaging lenssatisfies the following conditional expression (8):1.00<R4/f2<30.00  (8) where R4 is a paraxial curvature radius of asurface on the object side of the second lens.
 6. An imaging apparatuscomprising: an imaging lens; and an imaging device which converts anoptical image formed by the imaging lens into an electrical signal,wherein the imaging lens includes an aperture stop, a first lens havinga positive refractive power, a second lens having a negative refractivepower which is formed in a concave shape on both sides thereof, a thirdlens having a positive refractive power which is formed in a meniscusshape in which a concave surface is directed toward the side of anobject, and a fourth lens having a negative refractive power in which aconvex surface is directed toward the object side, which aresequentially disposed from the object side to the image side, andwherein the imaging lens satisfies the following conditional expressions(1), (2), (3), (4) and (5):0.40<f1/|f2|<0.80  (1)0.80<|f2|/f3<1.50  (2)0.90<f/|f4|<2.00  (3)2.60<|(R2−R3)/f1|<4.00  (4)νd1−νd2>25  (5) where f1 is a focal length of the first lens, f2 is afocal length of the second lens, f3 is a focal length of the third lens,f4 is a focal length of the fourth lens, f is a focal length of anentire lens system, R2 is a paraxial curvature radius of a surface onthe object side of the first lens, R3 is a paraxial curvature radius ofa surface on the image side of the first lens, νd1 is an Abbe number ofthe first lens, and νd2 is an Abbe number of the second lens.